Abstract
An modified E-shaped dual-mode resonator is proposed to design two types of dual-mode bandpass filters such as Filter I and Filter II. The proposed resonator comprises of a half-wavelength hairpin resonator and a meander ring on its symmetrical plane. As the structure is symmetrical, it supports odd and even mode theory. In Filter I, based on coupling gaps between feedlines and middle arm of E-shaped resonator, the location of upper stopband transmission zero is controlled. Using two tuning stubs incorporated with inner meander ring, passband center frequency and bandwidth are controlled in Filter II. Additional transmission zero is procured in upper stopband using source load coupling scheme to improve the selectivity of the filter. Both filters are designed for passband center frequency 2.5 GHz and fractional bandwidth 0.4.
